Spinal fluid introduction

ABSTRACT

A fluid introduction system includes an introducer configured to create a pressure of at least 69 kPa within a spine, and an operator configured to actuate the introducer to introduce fluid into the spine according to a predetermined fluid introduction profile. The system can include a computer readable medium having code for receiving fluid introduction data indicative of a fluid introduction parameter, and for receiving response data indicative of a response of the patient at a time related to a time of the fluid introduction data. A method for introducing fluid includes positioning a first introducer in a first portion of a spine, positioning a second introducer in a second, different portion of the spine and, without removing the first and second introducers, introducing fluid into the first portion of the spine with the first introducer and introducing fluid into the second portion of the spine with the second introducer.

RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.10/782,900, filed Feb. 23, 2004, which claims priority under 35 U.S.C.§119 to U.S. provisional application no. 60/448,529, filed Feb. 21,2003. Each related application is incorporated by reference herein inits entirety.

TECHNICAL FIELD

The present invention relates to a system and method for introducingfluid into a spine.

BACKGROUND

Back pain is a common problem and is difficult to treat. Because of thecomplex anatomy and poor correlation of pathology and symptoms,diagnosis of the etiology of the pain may be difficult. Typicaldiagnostic procedures seek to determine whether a patient experiencesback pain, leg pain, or a combination thereof. Back pain describes painlocalized to the back, and often includes pain in the buttocks and upperthigh areas. This type of pain is understood to be caused by changes inone or more intervertebral discs and is termed discogenic back pain. Therecognition that discs are potential pain sources has been a relativelyrecent discovery and is supported by anatomical studies that demonstratenerve fibers within the disc, often increased by degenerative processes,and by direct stimulation of discs during discectomy procedures whilethe patient is under aware-state analgesia. Other causes of back painhave also been described including zygopophyseal (facet) joints, andother unknown causes.

In contrast, leg pain is often due to impingement of nerve roots as theyexit the spinal canal. This causes pain to radiate into the areas thenerves innervate and creates a dermatomal pattern of pain related to thenormal pattern of the nerve supply. This radicular pain is often due toherniation of intervertebral discs such that they bulge into theforamenal space, entrapping and pressing on the nerve. It is alsobelieved to result from nucleus pulposus material extruding from thedisc, resulting in noxious stimuli from degradation products such asphospholipase A2, and cytokines such as interleukins and TNFa.

Because the treatments for back pain and leg pain are often different,it is important to establish a proper diagnosis. Indeed, there is astrong correlation between patient selection and outcomes for spinalprocedures, such that meticulous attention to diagnosis is essential.This is especially true as patients often exhibit a pattern of symptoms.Even sophisticated imaging capabilities do not always provide a cleardiagnostic picture. Other diagnostic tools, such as physical examinationand determination of patient history, are important.

A staple of physical examination is palpation of the painful region, topinpoint where the pain is emanating from. This is difficult in the caseof the intervertebral disc as it is anatomically located deep within thebody and surrounded by bony structures. A procedure known asdiscography, discogram, disc stimulation, or more precisely asprovocative discography, has been developed to overcome this limitation.Discography involves placing a needle into the intervertebral disc usingfluoroscopic guidance and then injecting a fluid to create pressure tostimulate the disc, analogously to palpation. The injected fluid istypically a saline solution including radiopaque dye to allow forassessment of the disc morphology. A manually operated syringe isgenerally used to inject the fluid. The patient is maintained in anaware state such that they can provide feedback as to the pain inducedby the injection, i.e. pressurization of the disc. Injection isperformed one disc level at a time with the injectionist, e.g., aphysician, switching connections prior to the start of the test at aspecific level.

Pressure manometry has been used to monitor the pressure applied to thedisc. This provides a more objective means for the injectionist tocontrol pressure as compared to determining the pressure based upon thefeel of a manually operated syringe. Studies have demonstrated a betterdiagnostic correlation when patients respond to low to moderatepressures (<50 psi) as compared to higher pressures (>50 psi).

Another aspect of performing a reliable discography diagnosis is how theinjectionist interacts with the patient to obtain feedback on the painstimulation. A patient's response to pain can include two components:the magnitude of pain and the quality of pain. The magnitude is oftendescribed as ranging from 0 to 10, where 0 is no pain, and 10 is theworst pain imaginable. The quality of pain is described as beingconcordant, meaning the back pain they are complaining of, or notconcordant, pain different from their complaint, such as a generalfeeling of pressure. The ability to distinguish between concordant andnon-concordant pain improves the determination of whether the disc beingstimulated is the root cause of a patient's back pain, or is evokingpain unrelated to their symptoms. A low pressure, concordant painresponse at 1 or 2 spine levels, e.g., spinal discs, accompanied by nopain at a level above or below (control level) the painful discs isgenerally understood to provide the most definitive diagnosis fordiscogenic pain.

Patient responses from a discography procedure are recorded by theinjectionist or assistant using one or more forms. Other parameters,such as the volume of fluid injected are added to the patient responses.A separate chart can be used to determine the peak pressure in the discas well as any leakage.

SUMMARY

One aspect of the present invention relates to a fluid introductionsystem. In one embodiment, the fluid introduction system includes wanintroducer configured to create a pressure of at least 10 psi (69 kPa)within a spine, and an operator configured to actuate the introducer tointroduce fluid into the spine according to a predetermined fluidintroduction profile.

Embodiments of this aspect of the invention may include one or more ofthe following features:

The introducer can be configured to create a pressure of at least 10 psi(69 kPa) in an intervertebral disc.

The predetermined fluid introduction profile can be the introduction offluid at a constant rate. The introducer can be configured to introducea repeatable amount of fluid into the spine. The introducer can beconfigured to introduce fluid into the spine at a repeatable rate. Theintroducer can be configured to introduce a non-pulsatile flow of fluidinto the spine. The introducer can be configured to create a pressure ofat least 20 psi (138 kPa) in an intervertebral disc.

According to another aspect of the invention, a fluid introductionsystem comprises an introducer configured to introduce fluid into aspine of a patient, an operator configured to actuate the introducer tointroduce fluid into the spine of the patient, a computer readablemedium having code for receiving fluid introduction data indicative of afluid introduction parameter, and for receiving response data indicativeof a response of the patient at a time related to a time of the fluidintroduction data.

Embodiments of this aspect of the invention may include one or more ofthe following features:

The fluid introduction parameter can be a pressure within anintervertebral disc of the patient at the time of the fluid introductiondata and/or a total amount of fluid introduced into an intervertebraldisc of the patient at the time of the fluid introduction data.

The fluid introduction parameter can be configured to obtain theresponse data from an observation of the patient and/or to obtain theresponse data upon a response by the patient.

The fluid introducer can be configured to create a pressure of at least100 kPa within the spine.

According to another aspect of the invention, a fluid introductionsystem includes an introducer configured to introduce a non-pulsatileflow of fluid into a spine, and an operator configured to actuate theintroducer. The introducer has a flow rate-dependent impedance opposingthe introduction of the fluid. The operator includes code to control theactuation of the introducer based at least in part upon impedance dataindicative of the impedance.

Embodiments of this aspect of the invention may include one or more ofthe following features:

The introducer can include an identifier including the impedance dataand the operator can be configured to receive the impedance data fromthe identifier of the introducer. The operator can include code todetermine the impedance data based upon an actuation of the introducer.

The fluid introduction system can include a pressure sensor configuredto provide pressure data indicative of a pressure of fluid present inthe introducer, a fluid introduction sensor configured to provide fluidintroduction data indicative of at least one of (a) a rate of fluidintroduction and (b) an amount of fluid dispensed from the introducer,and the operator can include code to determine the impedance data basedupon the pressure data and the fluid introduction data.

According to another aspect of the invention, a fluid introductionsystem includes a first introducer configured to introduce fluid into afirst portion of a spine, a second introducer configured to introducefluid into a second, different portion of a spine, and an operatorconfigurable to concurrently actuate the introduction of fluid into thefirst portion of the spine by the first introducer and the introductionof fluid into the second portion of the spine by the second introducer.

Embodiments of this aspect of the invention may include one or more ofthe following features:

The first and second introducers can be respectively configured tointroduce fluid into first and second different intervertebral discs,such as to provide a simultaneous pressure of at least 10 psi (69 kPa)in each of the first and second intervertebral discs. The first andsecond introducers can be actuable independently of one another.

According to another aspect of the invention, a fluid introductionsystem includes an introducer configured to introduce a fluid having adynamic viscosity of at least 750 Pa into a spine and an operatorconfigured to actuate the introducer according to a predeterminedintroduction profile.

Embodiments of this aspect of the invention may include one or more ofthe following features:

The fluid can be at least one of a polymeric fluid and a non-Newtonianfluid.

The introducer can have an impedance that opposes the actuation of theintroducer, the impedance is, e.g., dependent upon the viscosity of thefluid and the fluid introduction system can be configured to obtainimpedance data indicative of the dynamic viscosity of the fluid.

According to another aspect of the invention, a syringe includes areservoir, a plunger slidable with respect to the reservoir to applypressure to fluid therein, and a pressure transducer secured withrespect to the plunger such that the pressure transducer is in directcontact with fluid in the reservoir.

Embodiments of this aspect of the invention may include one or more ofthe following features:

A receivable portion of the plunger can be receivable within thereservoir. The syringe can include a cap secured with respect to thereceivable portion of the plunger. The pressure transducer can bedisposed between at least a portion of the cap and at least a portion ofthe receivable portion of the plunger.

The cap can include a hole configured to allow fluid present within thereservoir to contact the pressure transducer.

The cap and the plunger can be configured so as not to be rotatable withrespect to one another when the cap is secured with respect to thereceivable portion of the plunger.

The cap and the receivable portion of the plunger can each comprise anasymmetrical portion. The asymmetrical portions of the cap and plungercan mate with one another to secure the cap with respect to the plunger.

The cap can comprise a resilient material that provides a seal withinthe syringe.

The plunger can comprise a shaft, a first contact, a conductor extendingalong the shadt, and a second contact configured to mate with anactuator arm and to communicate pressure data from the pressuretransducer.

The cap can define a passage such that the pressure transducer is indirect contact with fluid in the reservoir via the passage. The cap canalso comprise a gasket seal surrounding the passage to provide a sealaround the pressure transducer.

The plunger can comprise projections and the cap can comprise notchesfor receiving the projections to join the plunger and cap together. Thecooperation between the projections and the notches can secure thepressure transducer on at least two sides. The projections and thenotches can be asymmetric so that the cap and the plunger are securedtogether in only one orientation. The plunger can also comprise anasymmetric butt such that the plunger can be positioned in only oneorientation with respect to a fluid delivery device.

According to another aspect of the invention, a fluid introductionsystem includes an introducer configured to introduce a fluid into aspine, and an operator configured to actuate the introducer to introducefluid into the spine according to a predetermined fluid introductionprofile.

According to another aspect of the invention, a method for introducingfluid includes positioning a first introducer in a first portion of aspine, positioning a second introducer in a second, different portion ofthe spine and, without removing the first and second introducers,introducing fluid into the first portion of the spine with the firstintroducer and introducing fluid into the second portion of the spinewith the second introducer.

Embodiments of this aspect of the invention may include one or more ofthe following features:

The first and second portions of the spine can be differentintervertebral discs.

Introducing fluid into the first portion of the spine can includecreating a pressure of at least 10 psi (69 kPa) in the first portion ofthe spine, and introducing fluid into the second portion of the spinecan include creating a pressure of at least 10 psi (69 kPa) in thesecond portion of the spine. Introducing fluid into the first portion ofthe spine can at least partially overlap the step of introducing fluidinto the second portion of the spine.

Advantages of the invention may include one or more of the following:

Positioning at least two introducers is advantageous over removing andreinserting a needle because such movement can cause the patient toanticipate pain. Additionally, the present system and method reduces therisk of infection because a syringe need be connected and removed onlyonce during the procedure. Use of multiple introducers decreases thetime required to perform a discography diagnostic by reducing the needfor switching the injection system between needles, and increases thedegree of flexibility for testing and retesting various levels.

A method and system have been developed that improves the overallquality of introduction of fluid into the spine, e.g., duringdiscography, vertebroplasty, and/or nucleus augmentation. With respectto discography, the improvement includes the ability to perform the testin a more reproducible manner, improving clinical efficacy.

The current system has design features that allow for a morestandardized procedure with regards to patient interaction and feedbackon pain responses. This is achieved by having a standardized dialog forthe injectionist and patient such that the injectionist does not provideinadvertent cues to the patient that could influence the patient'sresponse, and that instructs the patient concerning their role in theprocedure. Properly “blinding” the patient as to when injections areperformed is an example of how to avoid responses that could negativelyinfluence the value of the procedure. There is a substantialpsychological component of pain, and this appears to be exacerbated inchronic pain sufferers such as many people with back pain. A patientinterface module of the system is also an embodiment. This includes atouch panel screen where the patient traces pain as to intensity andquality (concordant or not). Another embodiment is a squeeze bulb forintensity of pain.

Another aspect of performing a standardized provocative disc diagnosisinvolves management of the data such that a diagnostic report can begenerated.

The system of the current invention has a central data logger thatcorrelates pressure, flow and volume readings from a syringe manometrydevice with the injection sequence and patient response data. Thiscentral processor further performs a diagnostic algorithm such asdescribed by the ISIS (International Spine Injection Society) Guidelines(modified to incorporate the more robust data provided with thisenhanced system), such that a diagnostic report is generated. Thecentral processor has user interfaces such as a key board that allowsfor entry of patient name, age, sex, date, and other key demographic andprocedure information such that reporting, billing and other functionsare expeditiously performed.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a fluid introduction system;

FIG. 2 is an illustration of the fluid introduction system of FIG. 1;

FIG. 3 is an illustration of the fluid drive assembly of the fluidintroduction system of FIG. 1;

FIG. 4 is an illustration of sub-systems of the fluid introductionsystem of FIG. 1;

FIGS. 5 and 6 are illustrations of flow rate graphs;

FIG. 7 is a side-view of a plunger and cap with pressure transducer;

FIG. 8 is an illustration of the plunger of FIG. 7 with the cap andpressure transducer removed;

FIG. 9 is a front view of the plunger of FIG. 8;

FIG. 10 is a rear view of the cap of FIG. 7 with the plunger andpressure transducer removed.

FIG. 11 is a schematic illustration of an alternative fluid introductionsystem;

FIG. 12 is an illustration of an embodiment of the fluid introductionsystem of FIG. 11;

FIG. 13 is an illustration of another embodiment of the fluidintroduction system of FIG. 11; and

FIGS. 14 and 15 are illustrations of flow profiles.

DETAILED DESCRIPTION

Referring to FIG. 1, a fluid introduction system 20 includes anintroducer 22 and an operator 24. Introducer 22 introduces fluid into aspine 28, such as into a vertebral body 29 or an intervertebral disc 30thereof. Operator 24 actuates the introduction of fluid by introducer22, preferably according to a fluid introduction profile.

Referring also to FIG. 2, introducer 22 includes a fluid drive assembly32 and a fluid introduction assembly 34. Fluid drive assembly 32includes a fluid reservoir, e.g., a 30 ml syringe 36, a pressureapplicator, e.g., a plunger 38 slidably received within syringe 36, forapplying pressure to fluid therein, an actuator arm 40 for movingplunger 38, and a motor 42 for driving actuator arm 40. Fluidintroduction assembly 34 includes a fluid introduction member, e.g., aneedle 44 for positioning in spine 28, and tubing 46 interconnectingsyringe 36 and needle 44 via a connector 45. Syringe 36 connects totubing 46 via a fitting, e.g., a Luer lock fitting, or syringe 36 andtubing 46 can be otherwise mechanically or adhesively secured. Tubing 46has a length of about 1.75 meters. Introduction assembly 34 includes apressure transducer 77 for providing pressure data indicative of apressure within assembly 34 and a remote control 79 to receive an eventmarker input from a user and allow the user to control system 20 such asby initiating, stopping, or pausing the introduction of fluid andsetting fluid introduction parameters. Remote control 79 can be inhardwired or wireless communication with operator 24 and can be integralwith system 20 or mechanically free thereof. Introducer 22 and operator24 are securely supported by a support 213 and a base 215.

Referring to FIG. 3, motor 42 is, e.g., an electric motor, such as theHaydon Switch and Instruments size 17 no. E43H4A-05 stepper motor(Waterbury, Conn.). Fluid drive assembly 32 includes a drive screw 48secured to an output shaft 50 of motor 42, and rotatably coupled to adrive nut 52. Drive screw 48 is supported by a fluid drive bracket 58and two support shafts 54 coupled to drive screw 48 by bearings 56 a, 56b. Bearings 56 a, 56 b are coupled to drive nut 52 to move linearly withdrive nut 52. Axial movement of drive nut 52 is transferred to actuatorarm 40 by bearings 56 a, 56 b. Support shafts 54 distribute the loadapplied to drive screw 48. Motor 42 is reversible such that the fluidcan be introduced and extracted from the spine using system 20.

Referring to FIG. 4, fluid introduction system 20 includes a number ofsub-systems, e.g, fluid drive assembly 32 of introducer 22, and operatorcontrol subsystem 60, pressure monitoring 62, data acquisition 64,patient feedback 66, user interface 68, and test report 70 of operator24. These subsystems and other aspects of the present invention arediscussed below.

Introducer

Referring again to FIGS. 1 and 2, introducer 22 introduces fluid to aspine, such as into a disc or vertebral body thereof. Introducer 22minimizes variations from test to test in the amount of fluid introducedand/or the pressure created within the spine, which can occur due totubing variables or volume changes and allows for corrections due topressure losses at, for example, connector 45. System components exhibitminimal volume change upon pressurization to about 100 psi (690 kPa), toabout 150 psi (1035 kPa), e.g., to about 200 psi (1380 kPa). System 20is preferably configured to generate a pressure in a spine of at leastabout 10 psi (69 kPa), 20 psi (138 kPa), 50 psi (245 kPa), 100 psi (690kPa), 150 psi (1035 kPa), e.g., at least about 200 psi (1380 kPa). Thus,operator 22 can use movements of the motor 42 to determine volume dataindicative of the volume of fluid introduced into the spine, preferablyto within 0.1 ml. A given volume of fluid can be repeatedly introducedwith a standard deviation of about 0.2 ml or less, such as about 0.1 mlor less. Introducer 22 dispenses the fluid at a minimum rate of 0.05 mls⁻¹. For example, introducer 22 can introduce a total volume of at leastabout 20 ml of fluid at from 0.1 ml s⁻¹ to 1 ml s⁻¹, such as in 0.1 mls⁻¹ increments. Introducer 22 is preferably configured to introduce anon-pulsatile flow of fluid, e.g., a given volume of fluid, e.g., atleast 0.3 ml or at least 0.5 ml, can be introduced at a pressure of atleast 15 psi with the volume of fluid being introduced with a relativevariation in flow rate of less than 10%, e.g., less than 5%.

Introducer 22 can introduce any of various fluids including but notlimited to Newtonian fluids, non-Newtonian fluids, and polymeric fluidsinto a spine. For example, the fluid can be a typical discography fluid,such as a saline solution optionally including a radio-opaque contrastagent. Alternative fluids include a hardenable medium, such as bonecement, and a hyrdrogel, such as used in nucleus augmentation orreplacement. An exemplary bone cement includes a polymer, e.g.,polymethylmethacrylate, a contrast agent, e.g., sterile barium powder,and an antibiotic. The hardenable medium can have a dynamic viscosity ofat least 250 Pa, 500 Pa, 750 Pa, 1000 Pa, such as at least about 1200Pa.

Pressure Monitoring Subsystem

Pressure monitoring subsystem 62 determines the pressure of fluidpresent within introducer 22 and provides pressure data for use by theoperator control subsystem 60 in feedback control loops. Pressuremonitoring subsystem 62 includes at least one pressure transducer and isdiscussed in more detail with respect to operator control subsystem 60and syringe 36. The pressure transducer is located within introducer 22,such as in fluid introduction assembly 34 or fluid drive assembly 32,preferably in direct contact with fluid present within introducer 22.Pressure data can include, for example, pressure versus time data, acracking pressure (the pressure at which internal pressure within thedisc is overcome and fluid begins being introduced) of an intervertebraldisc, and a maximum pressure created. Each of these pressure datapreferably include a time component indicative of a time at which theparticular pressure occurred.

System 20 is preferably configured to determine the cracking pressure ofa spinal disc. For example, the cracking pressure can be determined bymonitoring the pressure of fluid within introducer 22 as pressure isapplied to syringe 36. When the cracking pressure is reached, a pressurevariation, such as a pressure drop, occurs. System 20 can mark thecracking pressure and time the cracking pressure was reached as an eventthat can be reported using report sub-system 70 discussed below.

Operator Control Subsystem

Operator control sub-system 60 improves the repeatability and accuracyat which the fluid is introduced into the spine and allows for variousfluid introduction modes. System 20 can be used in a manual mode or apreprogrammed mode. In the manual mode, the user controls the startingand stopping of system 20 as well as any pauses in fluid introduction. Auser interface 68 including a graphical interface 75 of operator 24accepts user inputs of control parameters, test conditions, e.g., thedisc or disc to be tested, and provides the user with real time dataindicative of at least one of fluid pressure (pressure data), an amount(e.g., volume) of fluid introduced (volume data), and a rate of fluidintroduction (rate data). Pressure data indicative of the pressure offluid within introducer 22 is obtained from a pressure transducer, asdiscussed below. Volume data indicative of the amount of fluidintroduced is obtained from the actuation of syringe 36 by motor 42.Rate data indicative of the rate of fluid introduction is determinedfrom the volume data as a function of time. Each of the volume and ratedata preferably includes a time component indicative of a timeassociated with the particular data.

Graphical interface 75 displays data indicative of system 20 parameters,e.g., fluid introduction parameters related to the introduction offluid, during a test. For example, real time pressure data, volume data,and rate data can be displayed graphically, numerically, or throughcombination thereof. The location of the disc or disc into which fluidis being introduced can be displayed. Event markers and patient responsedata can also be displayed, preferably by showing the temporalrelationship between the system 20 parameters and the event marker orpatient response.

In the preprogrammed mode, fluid is introduced according to apredetermined fluid introduction profile under microprocessor control,e.g, using computer code residing in a computer readable medium. Duringthe introduction of fluid according to a predetermined fluidintroduction profile, control subsystem 60 controls the introduction offluid to achieve a given fluid pressure, a given pressure profile,introduce a given volume of fluid, or introduce fluid at a given rate orrate profile as specified by the user or manufacturer. Fluidintroduction profiles calling for variable introduction according tothese parameters can be used. System 20 includes control loops, asdiscussed below, which can dynamically modify the introduction of fluidduring the introduction according to a predetermined fluid introductionprofile.

System 20 can be configured to switch between the control of fluidintroduction according to a given combination of parameters, e.g., oneor more of pressure, volume, and rate, and control of fluid introductionaccording different combination of such parameters. For example, system20 can allow introduction of fluid according to one combination ofparameters until the cracking pressure of a disc is reached and thenswitch the introduction of fluid according to a different combination ofparameters thereafter. The switch can be initiated by system 20 or auser thereof.

The control sub-system 60 incorporates pressure, volume, and/or ratefeedback control loops, e.g., proportional-integral-derivative (PID)control loops, to control the fluid introduction based upon pressuredata, volume data, or rate data, respectively. Of course, a feedbackcontrol loop can utilize a combination of these and other parameters tocontrol the fluid introduction. For example, during fluid introduction,increased resistance to the fluid introduction can cause a pressureincrease. Control sub-system 60 includes a feedback loop configured toreduce a rate of advance of actuator arm 40 until the measured pressurereturns to a value within a predetermined range. Control sub-system 60can also include a feedback loop that notifies a user of a pressuredecrease, which can be indicative of a pressure loss or leak. The usermaintains a manual override during preprogrammed fluid introduction. Allcontrol loops discussed herein can be implemented as computer coderesiding in a computer readable medium.

As discussed above, a pressure variation can occur when the crackingpressure of a disc is reached during a test. Control sub-system 60 caninclude a control loop to minimize fluctuations in the rate of fluidintroduction that might otherwise result from the pressure variation.For example, if a drop in pressure occurs, the control loop can reducethe actuation rate of motor 42 to compensate for the pressure drop inpressure. Thus, system 20 can maintain the introduction of fluid at aconstant rate.

Operator control sub-system 60 can correct the pressure data fordifferences between the pressure created within a spine by theintroduction of fluid and the pressure of the fluid within introducer22. A variable that can cause such differences is the resistance tofluid introduction caused by the impedance of the syringe 36 and fluidintroduction assembly 34. For example, tubing with a narrower boreand/or longer length will have a higher impedance than tubing with awider bore and/or shorter length. Also, a needle with a narrower boreand/or longer length will have a higher impedance than a needle with awider bore and/or shorter length. During the introduction of fluid, theimpedance can cause the pressure data from the introducer to be higherthan the actual pressure created in the spine. Operator controlsubsystem 60 includes control loops that correct the pressure data basedupon impedance data indicative of the impedance to fluid introduction offluid introduction assembly 34 and syringe 36. Exemplary impedance dataare indicative of the resistance to fluid flow of the syringe and fluidintroduction assembly and can include, e.g, at least one of the gauge ofthe needle, the length of the needle 44, the inner diameter of thetubing, and the length of tubing 46.

The impedance data can be determined on the basis of the properties ofthe syringe and fluid introduction assembly 34, empirically, or by acombination thereof. For example, as discussed below, introducer 22,e.g., syringe 36, can include the impedance data. Empiricaldetermination of the impedance data can be performed as follows.Operator control subsystem 60 actuates fluid drive assembly 32 by anamount sufficient to dispense a given amount of fluid. The actuation ispreferably performed prior to inserting needle 44 into a spine. Pressuredata are obtained during the actuation. The impedance data aredetermined based upon the pressure during actuation and the volume offluid dispensed. Operator control subsystem 60 allows fluid variablesincluding viscosity to be input for use in empirical impedancedetermination.

As discussed above, system 20 can be used to introduce hardenable media,e.g., bone cements, into a spine, such as in vertebroplasty. Theviscosity of a hardenable medium increases as it cures and the medium ispreferably not introduced into the spine until having reached apredetermined viscosity. Operator control subsystem 60 includes aviscosity determination control loop to determine when the hardenablemedium has reached the predetermined viscosity suitable forintroduction. Prior to introducing the hardenable medium into the spine,the viscosity determination control loop actuates the fluid drivesubsystem to dispense a given amount of the hardenable medium andpressure data are obtained during the dispensation. The resistance ofthe fluid to the dispensation appears as an increase in pressure withinthe introducer 22 and is a function of the viscosity of the hardenablemedium. The viscosity of the hardenable fluid is determined using thepressure data and calibration data for the particular hardenable fluid.Impedance data, as described above, may also be used in thedetermination of the viscosity.

Referring to FIGS. 5 and 6, fluid can be introduced according to anumber of different predetermined fluid introduction profiles. During acontinuous fluid introduction profile 80, a pressure within the spineand/or an amount of fluid introduced into the spine increasecontinuously between a starting point 82 and an end point 84. A slope 86of profile 80 can be varied. During preferred continuous fluidintroduction profiles, a rate of fluid introduction is constant, such asbetween starting point 82 and end point 84. Thus, a pressure within thedisc and the total volume of fluid introduced increase linearly.Non-linear fluid introduction profiles during which the rate of fluidintroduction varies can also be used.

As seen in FIG. 6, during a ramp fluid introduction profile 90, pressureincreases 92 within the spine to a first level 94 and is then held atthis level for a time and then pressure increases 96 to a second level98 and is then held for a period of time. First and second pressurelevels and the duration of time for which these levels are held can bearbitrary or predetermined. One or more additional pressure increases100 and holds 102 can be added until a desired upper pressure or volumelimit is reached. The increases in pressure can be at a constant orvariable rate as described above.

Syringe

Returning to FIG. 2, syringe 36 provides a reservoir for fluid to beintroduced into the spine and is preferably clear to allow a user todetermine the fluid level therein and ascertain the presence of bubbles.Plunger 38 slides with respect to syringe 36 to pressurize fluid thereincausing fluid introduction assembly 34 to dispense fluid. Referring alsoto FIGS. 7 and 8, plunger 38 includes a cap 39. Cap 39 is formed of aresilient material, e.g., a silicone-based material, to provide a sealsufficient to withstand pressures without substantial leakage of up to150 psi within syringe 36.

Cap 39 includes a pressure transducer 41, e.g., a piesoresistivepressure sensor, such as an ICSensors Model 1471 pressure transducer,and a passage 43 configured to place a pressure sensing portion 101 oftransducer 41 in direct contact with fluid present within syringe 36.Pressure transducer 41 provides pressure data indicative of a pressureof the fluid. Plunger 38 includes first contacts 47, a conductor 49extending along a shaft 69 of plunger 38, and second contacts 51 forcommunicating pressure data away from cap pressure transducer 41.Actuator arm 40 includes contacts 53 that mate with contacts 51 (FIG. 3)such that the pressure data are received by operator 24, which is incommunication with fluid delivery device 32. Transducer 41 preferablyprovides pressure data accurate to within 2% of the actual pressure overa range of 0-100 psig (0-690 kPa), e.g., 0-150 psig (0-1035 kPa). Asecondary pressure transducer can be used to act as a backup totransducer 41.

Cap 39 and plunger 38 securely seat pressure transducer 41 to limitleaks and loss of electrical connectivity during use. Cap 39 includes agasket seal 55 surrounding passage 43 and an inner wall 57 providing asecondary seal around the sides of the pressure transducer to limitfluid coming in contact with the electrical contacts of pressuretransducer 41 and plunger 38. Adhesive may be used to further securepressure transducer 41 with respect to cap 39 and to limit loss ofelectrical contact. First contacts 47 are preferably molded as part ofplunger 38 to provide a solder-less contact that reduces leakage andimproves electrical isolation.

Referring to FIGS. 9 and 10, plunger 38 includes projections 61 a, 61 band cap 39 includes notches 63 a, 63 b for receiving projections 61 a,61 b when the plunger and cap are mated. Additionally, cooperationbetween projections 61 a, 61 b and notches 63 a, 63 b secures pressuretransducer 41 on at least two sides to limit lateral motion with respectto cap 39 and plunger 38. Projections 61 a, 61 b and notches 63 a, 63 bare preferably asymmetric so that cap 39 can be secured to plunger 38 inonly one orientation. Cap 39 includes locating marks, e.g., locatingpins 59 so that pressure transducer 41 can be secured with respect tocap 39 in only one orientation. The asymmetric projections, notches andthe locating marks facilitate proper assembly of cap 39, plunger 38, andtransducer 41. The asymmetrical portions of the cap and plunger can matewith one another to secure the cap with respect to the plunger. Cap 39and plunger 38 are preferably not rotatable with respect to one anotherwhen the cap is secured with respect to the plunger.

Plunger 38 includes a butt 71 that can also be asymmetric so thatplunger 38 can be positioned in only one orientation with respect tofluid delivery device 32 thereby assuring proper communication betweencontacts 51 of plunger 38 and contacts 53 of actuating arm 40 (FIG. 3).Because contacts 51 of plunger 38 and contacts 53 of actuator arm 40 arebrought into electrical communication by positioning syringe 36, noadditional electrical contacts need be made by a user. Fluid deliverydevice 32 determines when contacts 53 of actuator arm 40 contactcontacts 51 of butt 71 of plunger 38 such that additional movement ofactuator arm 40 would pressurize syringe 36 and/or dispense liquid.Fluid drive subsystem 32 can also include a sensor (not shown) todetermine when actuator arm 40 has been fully extended.

As discussed above, syringe 36 and plunger 38 can include impedance dataindicative of an impedance to fluid introduction of syringe 36 and fluidintroduction assembly 34. In a preferred embodiment for a particularfluid drive assembly 32 and fluid introduction assembly 34 provided bythe manufacturer, impedance data are readout at contacts 51 of plunger38 by contacts 53 of actuator arm 40 (FIG. 4). For example, a particulararrangement of contacts 51 can be indicative of the impedance data.Thus, when a syringe, plunger, and fluid introduction assembly arepositioned for use in fluid delivery system 32, the impedance data areread at contacts 53 and received by operator 24. The operator controlsubsystem 60 includes control loops that control the introduction offluid based at least in part upon the impedance data. In one embodiment,the fluid introduction assembly 34 is a disposable assembly to bediscarded after a single use. In such an embodiment, operator 24 ispreferably configured to recognize each assembly and limit the assemblyto a single patient use.

Fluid introduction assembly 34, can include other data indicative ofproperties of the system, e.g., an expiration date of the assemblyand/or properties of fluid within the assembly, e.g., composition andviscosity, if preloaded by the manufacture. These data and the impedancedata may be encoded using, e.g., radio frequency identification, barcoding, and or an arrangement of contacts 51, as discussed above.Operator 24 can be configured, such as through computer code, to readthe data, e.g, expiration date data, and prevent use of an expired fluidintroduction assembly. Operator 24 can be configured, such as throughcomputer code, to read data indicative of properties of preloaded fluidand adjust fluid introduction profiles according to the properties ofthe preloaded fluid.

Data Acquisition

Data acquisition sub-system 64 increases the efficiency of system 20 bycollecting substantially all patient-related data in one location suchthat the patient-related data can be readily incorporated into a finalreport. Data acquisition subsystem 64 also allows for accurate and realtime data acquisition and monitoring facilitating the diagnosticcapability of fluid introduction procedures such as discography. Theseand other features of data acquisition sub-system 64 can be implementedby a computer readable medium including computer code.

Data acquisition subsystem 64 records user inputs, such as a patientidentifier, the location(s) of the spine receiving injected fluid, thenumber of locations receiving fluid, and the order of fluid introductioninto these locations. Other data, such as the cracking pressure of thedisc, maximum pressure reached in each disc, the presence of pressureleakage, equilibrium pressure in each disc, and volume of fluidintroduced can also be recorded. These data can be recorded in any oneof a number of digital media including flash cards, floppy discs, CDetc. The data acquisition subsystem also receives event marker inputs,such as from remote control 79. The event marker inputs may beindicative of a patient response observed by the user or other conditionto be noted.

Patient Feedback Sub-System

Patient feedback sub-system 66 receives real-time quantifiable responsedata of the patient. The response data preferably includes a patient'spain level and concordance and can include data input directly by thepatient using, e.g. a squeeze ball or a sliding device correlated to avisual analog scale (VAS) from 0-10 and including an axis for relatinglevel of concordance/non-concordance of the pain, and/or observed datasuch as physiological parameters including electromyographic responsedata. Other observed data include audiovisual recordings of facialresponses such as wincing, grimacing, clenching of the jaw and the like.

The response data is communicated to data acquisition sub-system andtemporally correlated with actual measurements of disc pressure and thevolume of fluid introduced into one or more discs. These and otherfeatures of patient feedback sub-system 66 can be implemented by acomputer readable medium including computer code.

Report Sub-System

Report sub-system 70 provides a final report that facilitates thediagnosis of the pain source and reimbursement procedures as well as theability to interface with other digital patient records, such as theSmith & Nephew digital OR system.

The report sub-system creates records of the procedure, and correlatesother imaging modalities such as fluoroscopy, CT and MRI scans into thepatient record. It also produces reports that have analyzed the data perprotocols that have been developed by professional societies such asISIS, NASS or reimbursing institutions. The data is in formats that canbe incorporated into other digital patient record management systemssuch as that used by the DOD. These and other features of reportsub-system 70 can be implemented by a computer readable medium includingcomputer code.

Reports provided by sub-system 70 allow a comparison of the temporalrelationship between event markers, a particular patient response,pressure and volume introduction data, and a state of fluid introductionsystem 20. Based on such reports, a user can discriminate between paincorrelated with the onset of fluid introduction and pain more stronglycorrelated with a particular pressure or volume introduced. The abilityto establish such temporal relationships among data acquired during adiagnostic procedure facilitates diagnostic accuracy.

Other embodiments are within the scope of the invention. For example,referring to FIG. 11, a fluid introduction system 120 includes anintroducer 122 having at least three, e.g., at least four, fluidintroduction assemblies 34 (each fluid introduction assembly is asdescribed above) and an operator 124 to actuate the fluid introductionassemblies of introduction system 120. Embodiments of introducer 122 aredescribed below as introducers 222 and 322.

Referring to FIG. 12, a fluid introduction system 220 includes anintroducer 222 having three fluid introduction assemblies 34 and a fluiddrive assembly 32, as described above, coupled to each of the threefluid introduction assemblies 34 through a manifold 115. Manifold 115defines an inflow channel 117 and three outflow channels 119. Locatedalong each outflow channel is a valve 121 and a pressure sensor 123,which can be used as an alternative or complement to locating a pressuresensor elsewhere within introducer 222. Valves 121 control the flow offluid from the fluid drive assembly 32 to each fluid introductionassembly 34. Operator 224 can be configured as described for operators22 and 122. Additionally, operator 224 is in feedback communication withthe valves 121 and pressure sensors 123 of manifold 115 and fluid driveassembly 32. Accordingly, operator 224 actuates valves 121 and fluiddrive assembly 32 to effect predetermined fluid introduction profiles byany combination of fluid introduction assemblies 34. Operator 224 alsodetermines the actuation of valves 121 and fluid drive assembly 32 basedupon pressure readings from pressure sensors 123. Introducer 222 ispreferably configured to generate a pressure in a spine of at leastabout 10 psi (69 kPa), 20 psi (138 kPa), 50 psi (245 kPa), 100 psi (690kPa), 150 psi (1035 kPa), e.g., at least about 200 psi (1380 kPa) ineach of at least three portions of a spine, e.g., at least four portionsof a spine.

Manifold 115 allows more than one needle 44 to be connected to thesyringe 36 prior to start of a fluid introduction procedure. Each needle44 can then be positioned with respect to the spine, e.g., at anappropriate disc level or vertebral body and the valves controlled tointroduce fluid sequentially or concurrently.

Referring to FIG. 13, a fluid introduction system 320 includes anintroducer 322 having three fluid introduction assemblies 34 (each fluidintroduction assembly is as described above) coupled to three fluiddrive assemblies 32, as described above. Introducer 322 is preferablyconfigured to generate a pressure in a spine of at least about 10 psi(69 kPa), 20 psi (138 kPa), 50 psi (245 kPa), 100 psi (690 kPa), 150 psi(1035 kPa), e.g., at least about 200 psi (1380 kPa) in each of at leastthree portions of a spine, e.g., at least four portions of a spine.

Fluid introduction systems 120, 220, and 320 allow a user to positiontwo or more fluid introduction assemblies 34 such that each of thepositioned assemblies is ready to introduce fluid into the spine, e.g.,into different intervertebral discs or different vertebral bodies. Then,using the positioned assemblies, the user can introduce fluid into thespine to create a simultaneous state of pressure in each two, three, ormore portions of the spine. Thus, the user can introduce fluid into twoor more different portions of the spine without removing orrepositioning the fluid introduction assembly from one of the portions.

Referring to FIG. 14, using pressure or volume feedback control, therate of increase of pressure or volume at each of three disc levels canbe controlled such that each disc level is concurrently stimulated atdifferent levels. Alternatively, as shown in FIG. 15, each disc levelcan sequentially be stimulated to the same level. Thus, the introductionof fluid into different portions of the spine can be concurrent,sequential, or partially overlapping in time.

What is claimed is:
 1. A syringe comprising: a reservoir; a plungerslidable with respect to the reservoir to apply pressure to fluidtherein; and a pressure transducer secured with respect to the plungersuch that the pressure transducer is in direct contact with fluid in thereservoir.
 2. The syringe of claim 1, wherein a receivable portion ofthe plunger is receivable within the reservoir and the syringe comprisesa cap secured with respect to the receivable portion of the plunger, thepressure transducer being disposed between at least a portion of the capand at least a portion of the receivable portion of the plunger.
 3. Thesyringe of claim 2, wherein the cap comprises a hole configured to allowfluid present within the reservoir to contact the pressure transducer.4. The syringe of claim 2, wherein the cap and the plunger are notrotatable with respect to one another when the cap is secured withrespect to the receivable portion of the plunger.
 5. The syringe ofclaim 4, wherein the cap and the receivable portion of the plunger eachcomprise an asymmetrical portion, the asymmetrical portions of the capand plunger mating with one another to secure the cap with respect tothe plunger.
 6. The syringe of claim 2, wherein the cap comprises aresilient material that provides a seal within the syringe.
 7. Thesyringe of claim 1, wherein the plunger comprises a shaft, a firstcontact, a conductor extending along the shaft, and a second contactconfigured to mate with an actuator arm and to communicate pressure datafrom the pressure transducer.
 8. The syringe of claim 2, wherein the capdefines a passage such that the pressure transducer is in direct contactwith fluid in the reservoir via the passage.
 9. The syringe of claim 8,wherein the cap comprises a gasket seal surrounding the passage toprovide a seal around the pressure transducer.
 10. The syringe of claim2, wherein the plunger comprises projections and the cap comprisesnotches for receiving the projections to join the plunger and captogether.
 11. The syringe of claim 10, wherein cooperation between theprojections and notches secure the pressure transducer on at least twosides.
 12. The syringe of claim 10, wherein the projections and thenotches are asymmetric so that the cap and the plunger are securedtogether in only one orientation.
 13. The syringe of claim 1, whereinthe plunger comprises an asymmetric butt such that the plunger ispositioned in only one orientation with respect to a fluid deliverydevice.